The present invention relates to the component parts of pumps, in particular of centrifugal drain pumps for dishwashers, provided with a cutting and tearing device coupled to the pump, for the grinding of waste carried by the washing water.
Water re-circulation pumps that have a device coupled to the rotary shaft of the pump for cutting and tearing up or grinding the food waste borne by the washing water are known in dishwashers for the purpose of preventing said waste from blocking the sprayer. The waste is channeled to a collection chamber adjacent to the pump impeller and it is retained there after being ground by the cutting device until discharged by the drain pump at the end of the washing cycle. On dishwasher appliances provided with a grinder, the drain pumps have a filter built into the discharge pipe for holding back waste material.
U.S. Pat. No. 4,448,359 and U.S. Pat. No. 4,795,102 disclose centrifugal water re-circulation and drain pumps in a dishwasher appliance, wherein the pump impeller has a waste grinding device coupled, adjacent to the pump drain cavity input.
DE-4423150 discloses a cutting device provided with a ring or tubular blade support coupled to the pump impeller shaft, where the blades are mounted conically at a given angle in relation to the shaft, forming a water swirl chamber which houses a similarly tubular member in its interior with bowed counter blades.
The object of the invention is to provide a grinding device for a dishwasher appliance drain pump, as defined in the claims. The grinding device according to the invention is of simple construction and can be easily coupled to the impeller of a common drain pump. It is not necessary to effect any modification in the structure of the drain pump.
The grinder device of the invention carries out thorough grinding of the waste, which enables the retaining filter that protects the pump to have a larger mesh or even permits dispensing with this filter. This grinding also prevents blockages in the pump and makes it possible for the waste reaching the drain circuit to be small enough not to cause problems in the drain circuit to which the dishwasher is coupled.
The grinder device covered by the invention includes a moving blade that rotates integral with the drain pump impeller and a fixed support adjacent to said blade, which has a plurality of apertures and is attached to the hydraulic body of the pump. The fixed support with its apertures acts as a fixed blade in combination with the moving blade, forming a moving bladexe2x80x94fixed blade assembly.
The gap between the moving blade and the fixed support is small and irrespective both of the assembly tolerances of the grinding device in the pump hydraulic body and of the pump impeller end play.